White light emitting diodes (LEDs) are known in the art and are a relatively recent innovation. It was not until LEDs emitting in the blue/ultraviolet of the electromagnetic spectrum were developed that it became practical to develop white light sources based on LEDs. As is known, white light generating LEDs (“white LEDs”) include a phosphor that is a photoluminescence material, which absorbs a portion of the radiation emitted by the LED and re-emits radiation of a different color (wavelength). For example the LED emits blue light and the phosphor re-emits yellow light. Alternatively the phosphor can emit a combination of green and red light, green and yellow or yellow and red light. The portion of the blue light emitted by the LED which is not absorbed by the phosphor mixes with the yellow light emitted to provide light which appears to the eye as being white. It is predicted that white LEDs could potentially replace incandescent light sources due to their long operating lifetimes, typically many 100,000 of hours, and their high efficiency. Already high brightness white LEDs are widely used in general lighting, street lighting, automotive applications, aeronautical applications, backlighting in LCD displays, laptops, tablets and cell phones.
The phosphor material that is used in the LED device is very carefully configured to have selected mixtures of different phosphor compositions at very particular loading percentages. This is because the exact color and quality of the light emissions from the LED device is highly dependent upon the type, quantity, and proportion of the phosphor compositions used in the device. Even slight variations in these parameters can cause a significant and visually perceptible change to the appearance of the light emissions from the device.
Difficulties may arise when phosphor manufacturers attempt to provide a consistent phosphor product to customers, where the phosphor product is a mixture of different phosphor materials in particle form at precisely calculated mixing percentages. The problem is that the process of storage and/or transporting of the phosphor product to the end-customer (e.g., the lighting manufacturer that incorporates the phosphor product into an LED device) may cause separation and settling of the phosphor particles to create mixture inconsistencies within the product.
To avoid these issues phosphor manufactures provide the customer with individual phosphors, which the customer then blends to achieve a desired color temperature of emitted light. However, many customers find it difficult to achieve consistent results with this approach since the end customers may not possess the correct equipment or expertise to achieve a mixture having a consistent distribution of the phosphor materials.
Therefore, there is a need for an improved approach to provide a phosphor product that avoids these and other problems.